Fluoropolymer resins, and especially perfluoropolymer resins, are known for their low surface energy and antistick properties and thermal and chemical resistance. These copolymers do not stick to other materials, especially dissimilar materials, with any practical degree of bond strength.
Some high temperature resistant thermoplastics (HTRP), such as polyamide imide, polyarylene sulfide and polyether sulfone, have found use as adhesion promoters in fluoropolymer coating formulations. See, for example U.S. Pat. No. 5,230,961 (Tannenbaum) and U.S. Pat. No. 5,093,403 (Rau el al.). However, such adhesion promoters are typically used in relatively high proportions which can detract from the properties of the fluoropolymer. For example, U.S. Pat. No. 5,230,961 claims (claim 7) a coated substrate wherein the primer contains 15-30% of polyamide imide and 25-55% of perfluoropolymer, and TABLE 14 of U.S. Pat. No. 5,093,403 gives primer formulations containing 15-20 wt % of polyphenylene sulfide or polyetheretherketone.
There remains a need for melt-flowable fluoropolymer with improved adhesion to dissimilar materials but which substantially retains the thermal and chemical resistance of fluoropolymer.